The axolotl, often called the Mexican walking fish, is an unusual salamander native only to a few lakes near Mexico City. These amphibians are almost exclusively aquatic, spending their entire lives underwater in a larval form. A rare biological pathway exists that can trigger a transformation, allowing them to develop traits necessary for life on land. The answer to whether an axolotl can live on land is complex: normally no, but sometimes yes, through metamorphosis.
The Default State: Why Axolotls Stay in Water
The primary reason axolotls remain aquatic is neoteny, meaning they reach sexual maturity without undergoing typical amphibian metamorphosis. This retention of juvenile features specializes them for an underwater existence. They keep feathery external gills, which are highly vascularized and serve as their primary means of extracting oxygen from the water.
Their skin is delicate and highly permeable, facilitating cutaneous respiration, or breathing through the skin. This permeable skin must stay constantly hydrated; exposure to air quickly leads to desiccation. Furthermore, their limbs are less developed, possessing rudimentary skeletal structure and muscle tone poorly suited for supporting their body weight against gravity. Without the physical and respiratory adaptations of a terrestrial salamander, the aquatic axolotl cannot survive outside of water for long.
Understanding Axolotl Metamorphosis
The potential for an axolotl to transition to a land-dwelling form exists because they possess the same developmental blueprint as their relative, the terrestrial tiger salamander. However, the natural process of metamorphosis is blocked by a lack of the necessary hormonal signal. Most amphibians rely on a surge of thyroid hormone, specifically thyroxine, to initiate the physical transformation into an adult form.
Axolotls typically do not produce the thyroid-stimulating hormone needed to prompt their thyroid gland to release sufficient thyroxine. This genetic difference keeps them in their neotenic, aquatic state. The transformation can be artificially induced in a laboratory by administering thyroxine or iodine compounds, bypassing the natural deficiency. Spontaneous metamorphosis may occur rarely in captivity, often linked to genetics or environmental stressors like poor water quality.
Physical Changes in the Terrestrial Axolotl
When an axolotl undergoes metamorphosis, it experiences physical changes to adapt to a terrestrial environment. The most noticeable change is the resorption of the external, feathery gills, which disappear into the gill slits. Simultaneously, the internal lungs, which were rudimentary in the aquatic form, develop significantly to support air breathing.
The body structure changes to allow for land movement, with the limbs and spine becoming robust to support weight. The skin becomes thicker and less permeable, developing a layered structure that helps the animal retain moisture. The axolotl also develops functional eyelids, which are absent in the aquatic form, and the dorsal fin along its back and tail is absorbed. The transformed animal looks like a small mole salamander and adopts a terrestrial method of locomotion, often showing an instinct to burrow into soil.